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DCS-3950 series Ethernet switch manual

Usage Guide: The lifetime of BPDU is called max age time. The max age is co working

with hello time and forward delay. The parameters should meet the following conditions.

Otherwise, the MSTP may work incorrectly.

2 * (Bridge_Forward_Delay - 1.0 seconds) >= Bridge_Max_Age

Bridge_Max_Age >= 2 * (Bridge_Hello_Time + 1.0 seconds)

Example: In global mode, set max age time to 25 seconds.

Switch(Config)#spanning-tree maxage 25

10.2.2.11 spanning-tree max-hop

Command: spanning-tree max-hop <hop-count>

no spanning-tree max-hop

Function: Set maximum hops of BPDU in the MSTP region; The command ‘no

spanning-tree max-hop’ restores the default setting.

Parameter: <hop-count> sets maximum hops. The valid range is from 1 to 40.

Command mode: Global Mode

Default: The max hop is 20 by default.

Usage Guide: The MSTP uses max-age to count BPDU lifetime. In addition, MSTP also

uses max-hop to count BPDU lifetime. The max-hop is digressive in the network. The

BPDU has the max value when it initiates from MSTI root bridge. Once the BPDU is

received, the value of the max-hop is reduced by 1. When a port receives the BPDU with

max-hop as 0, it drops this BPDU and sets itself as designated port to send the BPDU.

Example: Set max hop to 32.

Switch(Config)#spanning-tree max-hop 32

10.2.2.12 spanning-tree mcheck

Command: spanning-tree mcheck

Function: Force the port to run in the MSTP mode.

Command mode: Interface Mode

Default: The port is in the MSTP mode by default.

Usage Guide: If a network which is attached to the current port is running IEEE 802.1D

STP, the port converts itself to run in STP mode. The command is used to force the port

to run in the MSTP mode. But once the port receives STP messages, it changes to work

in the STP mode again.

This command can only be used when the switch is running in IEEE802.1s MSTP

mode. If the switch is running in IEEE802.1D STP mode, this command is invalid.

Example: Force the port 0/0/2 to run in the MSTP mode.

Switch(Config-Ethernet0/0/2)#spanning-tree mcheck

10.2.2.13 spanning-tree mode

Command: spanning-tree mode {mstp|stp}

no spanning-tree mode

Digitalchina Networks DCS-3950 series User Manual

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